A roadside bomb has killed at least 14 passengers travelling on a minibus in Afghanistan's western province of Herat, officials say.
The minibus was reportedly carrying members of a family on a wedding trip.
Earlier, a Nato airstrike in the southern province of Helmand killed four Afghan soldiers who were mistaken for militants, Afghan officials said.
The incidents come hours before US President Barack Obama delivers a review of his Afghan strategy.
A spokesman for the governor in Herat, Rafi Behrozan, told the BBC that the roadside bomb had struck the minibus in Kushk Kuhna district. The passengers were all members of an extended family, he said.
At least four people were wounded.
Mr Behrozan said security forces were at the scene and were ferrying the injured to hospital.
An officer with the National Directorate of Security in Herat told the BBC the attack took place on a busy road connecting Kushk Kuhna to Herat city. Two more bombs in the area had been defused, he said.
The officer said of the attack: "This is the work of the Taliban. They want to create a climate of fear among people."
Meanwhile, an International Security Assistance Force (Isaf) incident assessment team is looking into the Helmand attack.
"The incident occurred after a combined Afghan and Isaf patrol came under small-arms fire from insurgents," an Isaf statement said.
"The patrol called for a close air support mission in which a coalition aircraft positively identified the insurgent firing position and conducted an airstrike."
Helmand is one of the most violent regions of Afghanistan, with Nato troops battling Taliban rebels.
There have been other incidents of so-called "friendly fire" this year.
Three policemen died in August in northern Jowzjan province in a Nato airstrike. Another Nato air strike killed six Afghan soldiers in Ghazni province in July.
Later on Thursday, President Obama is expected to announce the findings of a report by his national security staff on progress in Afghanistan.
White House aides have suggested the report will contain few surprises and will support the president's intention to begin turning over security duties to Afghan forces in July 2011.
Afghan President Hamid Karzai said again on Wednesday that Nato should transfer full responsibility for all the country's affairs, including security, to Afghans by the end of 2014.
Ahead of the US report, two further assessments painted a bleak picture of the US-led war.
The Red Cross found armed groups were making life more difficult for Afghans.
And US intelligence assessments reported by the New York Times suggested there was a limited chance of success unless Pakistan hunted down insurgents.